Merge branch 'main' into text

1 files changed, 98 insertions, 0 deletions

diff --git a/exercises/advanced_errors/advanced_errs1.rs b/exercises/advanced_errors/advanced_errs1.rs
new file mode 100644
index 0000000..4bc7b63
--- /dev/null
+++ b/exercises/advanced_errors/advanced_errs1.rs
@@ -0,0 +1,98 @@
+// advanced_errs1.rs
+
+// Remember back in errors6, we had multiple mapping functions so that we
+// could translate lower-level errors into our custom error type using
+// `map_err()`? What if we could use the `?` operator directly instead?
+
+// Make this code compile! Execute `rustlings hint advanced_errs1` for
+// hints :)
+
+// I AM NOT DONE
+
+use std::num::ParseIntError;
+use std::str::FromStr;
+
+// This is a custom error type that we will be using in the `FromStr`
+// implementation.
+#[derive(PartialEq, Debug)]
+enum ParsePosNonzeroError {
+    Creation(CreationError),
+    ParseInt(ParseIntError),
+}
+
+impl From<CreationError> for ParsePosNonzeroError {
+    fn from(e: CreationError) -> Self {
+        // TODO: complete this implementation so that the `?` operator will
+        // work for `CreationError`
+    }
+}
+
+// TODO: implement another instance of the `From` trait here so that the
+// `?` operator will work in the other place in the `FromStr`
+// implementation below.
+
+// Don't change anything below this line.
+
+impl FromStr for PositiveNonzeroInteger {
+    type Err = ParsePosNonzeroError;
+    fn from_str(s: &str) -> Result<PositiveNonzeroInteger, Self::Err> {
+        let x: i64 = s.parse()?;
+        Ok(PositiveNonzeroInteger::new(x)?)
+    }
+}
+
+#[derive(PartialEq, Debug)]
+struct PositiveNonzeroInteger(u64);
+
+#[derive(PartialEq, Debug)]
+enum CreationError {
+    Negative,
+    Zero,
+}
+
+impl PositiveNonzeroInteger {
+    fn new(value: i64) -> Result<PositiveNonzeroInteger, CreationError> {
+        match value {
+            x if x < 0 => Err(CreationError::Negative),
+            x if x == 0 => Err(CreationError::Zero),
+            x => Ok(PositiveNonzeroInteger(x as u64)),
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn test_parse_error() {
+        // We can't construct a ParseIntError, so we have to pattern match.
+        assert!(matches!(
+            PositiveNonzeroInteger::from_str("not a number"),
+            Err(ParsePosNonzeroError::ParseInt(_))
+        ));
+    }
+
+    #[test]
+    fn test_negative() {
+        assert_eq!(
+            PositiveNonzeroInteger::from_str("-555"),
+            Err(ParsePosNonzeroError::Creation(CreationError::Negative))
+        );
+    }
+
+    #[test]
+    fn test_zero() {
+        assert_eq!(
+            PositiveNonzeroInteger::from_str("0"),
+            Err(ParsePosNonzeroError::Creation(CreationError::Zero))
+        );
+    }
+
+    #[test]
+    fn test_positive() {
+        let x = PositiveNonzeroInteger::new(42);
+        assert!(x.is_ok());
+        assert_eq!(PositiveNonzeroInteger::from_str("42"), Ok(x.unwrap()));
+    }
+}